Utilizing motion sensor data in past seafloor geodetic measurements

In the GPS/acoustic measurement, it is crucial to monitor precise position of an acoustic transducer or a surface platform in motion as a rigid body. A GPS gyro with 1 Hz sampling is not sufficient to accurately describe the transducer motion especially for our past system that used a small buoy, which has been upgraded into 10 Hz sampling at present system. Although the past system was equipped with an extra motion sensor, the data were not in use due to its incomplete configurations: unmeasured installation position/angle and lack of time stamp in the data. To utilize this awkward but important data, we developed an algorithm to solve these ambiguities all at once. The algorithm reveals the sensor position within 2 cm, the sensor angle within 0.4°, and time lag within 0.02 s precisions. Applying motion sensor data with setup conditions obtained through the algorithm, we successfully interpolate the transducer motion combined with the 1 Hz GPS gyro, which greatly reduces scatter in the travel times of acoustic ranging.